The overall incidence of postoperative vomiting between 25 and 30% for the pediatric population, but it can reach a much higher incidence associated with certain types of surgery, about 80% in some studies like strabismus surgery for example. The identification of patients at high risk of POV is possible through the use of risk score. It is currently only one pediatric validated risk score, but the investigators conducted a multicenter study on this subject, whose results are being analyzed. This should allow us to identify children at high risk of POV. In this targeted population, the prophylaxis should allow a significant reduction in the incidence of POV. In children only one study tried to evaluate the association of ondansetron, dexamethasone and droperidol to prevent postoperative vomiting. However, different doses of the different molecules were combined, the extremely complicated design of this study and important methodological bias do not provide evidence about the superiority of the combination of three anti-emetics compared with two anti-emetics. Our present randomized, double-blind study is designed to compare the effectiveness of Droperidol in combination with a conventional bi-prophylaxis (dexamethasone/ondansetron) to the conventional bi-prophylaxis alone to decrease the occurrence of postoperative vomiting in children at high risk. The combination ondansetron and dexamethasone is frequently assessed as an association to prevent postoperative vomiting also in the adult population and in the pediatric population.